By the Treaty of Compiègne in August 867,

King Charles the Bald Charles the Bald (french: Charles le Chauve; 13 June 823 – 6 October 877), also known as Charles II, was a 9th-century king of West Francia (843–877), king of Italy (875–877) and emperor of the Carolingian Empire (875–877). After a ser ...

ceded the peninsula of

Cotentin The Cotentin Peninsula (, ; nrf, Cotentîn ), also known as the Cherbourg Peninsula, is a peninsula in Normandy that forms part of the northwest coast of France. It extends north-westward into the English Channel, towards Great Britain. To its w ...

to King Salomon of Brittany. Though not specified in the treaty, the

Avranchin Avranchin is an area in Normandy, France corresponding to the territory of the Abrincatui, a tribe of Celts from whom the city of Avranches, the main town of the Avranchin, takes its name. In 867, by the Treaty of Compiègne, Charles the Bald gav ...

, including

Mont Saint-Michel Mont-Saint-Michel (; Norman: ''Mont Saint Miché''; ) is a tidal island and mainland commune in Normandy, France. The island lies approximately off the country's north-western coast, at the mouth of the Couesnon River near Avranches and is ...

, was likely included in the concession.

See also